The present invention generally relates to a fuel system and more particularly, to a vehicular fuel system which includes a variable volume fuel tank and which receives, stores, and selectively delivers pressurized fuel to an internal combustion engine without using a conventional fuel pump.
Vehicular fuel systems are adapted to selectively receive and store fuel for use within and/or by an engine (i.e., an internal combustion type engine), effective to allow a vehicle to be desirably driven and maneuvered.
Conventionally, these assemblies include a tank containing volatile or vaporific fuel, and an electric pump for delivering fuel from the tank to an internal combustion engine. Certain drawbacks, however, are associated with the use of these conventional fuel pumps. For example and without limitation, conventional fuel pumps often cause and/or allow undesirable fuel vapor bubbles to be formed within the fuel which reduce engine performance and efficiency.
Additionally, these prior types of fuel systems allow fuel which is stored within the tank to vaporize or evaporate. This fuel vapor collects above the fuel in the tank and may undesirably escape into the atmosphere. As a result of governmental regulation of emissions of this fuel vapor, automobile manufacturers have devised numerous methods and devices to selectively purge vapors from the tank, and to treat and controllably release such vapors into the ambient environment. These methods and devices undesirably add to the expense of the vehicle and may also allow some of the fuel vapors to undesirably escape into the atmosphere.
Attempts have been made to utilize a variable volume fuel tank for compressibly pressurizing the fuel within the tank in order to prevent fuel vaporization during the fuel delivery process. This type of variable volume fuel tank includes a piston which is movably disposed within the tank and which separates the tank into two volumes (e.g., one volume filled with fuel and one volume filled with pressurized air). The air is typically provided by a regulator which can be controlled by a microprocessor. The position of the piston is controlled in order to maintain the fuel at a relatively high pressure, thereby substantially reducing fuel vaporization. While this type of fuel delivery system solves many of the problems associated with conventional fuel systems, it does suffer from several drawbacks.
For example and without limitation, in order to prevent air from permeating the fuel, several relatively tight seals must be operatively disposed on the piston. These seals typically contact the housing of the tank and a guide rod on which the piston is disposed. These seals undesirably generate a relatively high amount of drag and may still allow an undesirable amount of air or vapor to permeate the fuel. Furthermore, these prior fuel systems utilize a spring and a pressure controlled clutch mechanism to allow the piston to retract during refueling. These clutch mechanisms undesirably increase the cost and complexity of the system. Moreover, these systems do not always provide sufficient delivery of fuel to the engine during system recharging and do not include a method or apparatus for extracting air that may be dissolved within and subsequently released from the fuel.
The present invention provides an improved pumpless fuel system which includes a variable volume fuel tank and which addresses the previously delineated drawbacks of prior fuel systems while concomitantly allowing fuel to be temporarily stored and communicated to an engine in an efficient and desired manner.
It is a first object of the present invention to provide a fuel system which overcomes at least some of the previously delineated drawbacks of prior fuel systems.
It is a second object of the present invention to provide a fuel system which includes a variable volume fuel tank for compressibly pressurizing the fuel within the fuel tank, thereby reducing the likelihood of undesirable fuel vapor emission.
It is a third object of the present invention to provide a fuel system which includes a variable volume fuel tank having a movable piston with reduced drag characteristics.
It is a fourth object of the present invention to provide a pumpless fuel system which includes an apparatus for extracting air that may be dissolved within and subsequently released from the fuel.
According to a first aspect of the present invention, a fuel system is provided. The fuel system includes a variable volume fuel tank including a first portion which selectively receives and contains an amount of fuel, and a second portion which selectively receives and contains an amount of pressurized gas; a piston which is movably disposed within the variable volume fuel tank; and at least one bellows member which is disposed within the tank, which at least partially defines the second portion of the tank, and which is coupled to a back surface of the tank, the at least one bellows member being selectively movable from a first contracted position to a second expanded position, the movement of the bellows member being effective to cause the piston to move within the variable volume fuel tank and to compressibly pressurize the amount of fuel.
According to a second aspect of the present invention, a method is provided for pressurizing an amount of fuel contained within a first portion of a fuel tank. The method includes the steps of providing a piston; movably disposing the piston within the fuel tank; providing at least one selectively expandable diaphragm; sealably connecting a first end of the at least one selectively expandable diaphragm to a back surface of the fuel tank, the at least one selectively expandable diaphragm being effective to define a second portion of the fuel tank which is sealably separated from the first portion of the fuel tank; and selectively introducing pressurized gas into the second portion of the fuel tank, effective to cause the at least one selectively expandable diaphragm to expand, thereby causing the piston to move within the variable volume fuel tank and to compressibly pressurize the amount of fuel.
These and other aspects, features, and embodiments of the present invention will become apparent from a reading of the following detailed description of the preferred embodiment of the invention and by reference to the following drawings.